JP2014007132A - Method for manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a nonaqueous electrolyte secondary battery by which gas generation can be suppressed while suppressing the increase in battery resistance.SOLUTION: A method for manufacturing a nonaqueous electrolyte secondary battery according to the invention comprises the steps of: forming an electrode body having a positive electrode including a positive-electrode active material, a negative electrode including a negative-electrode active material, and a separator disposed between the positive and negative electrodes; housing the electrode body in a battery container; and charging a nonaqueous electrolyte into the battery container, provided that the nonaqueous electrolyte includes lithium hexafluorophosphate, to which lithium difluorophosphate is added so as to have a density of 0.025-0.05 M. In this step, the adjustment is made so that the logarithm of the ratio R (R=A/B) of a content A(mol) of the added lithium difluorophosphate to a content B(mol) of moisture included in the electrode body before charging the nonaqueous electrolyte satisfies the following condition: -0.10<logR<0.

Description

  The present invention relates to a method for producing a non-aqueous electrolyte secondary battery.

  One non-aqueous electrolyte secondary battery is a lithium ion secondary battery. A lithium ion secondary battery is a secondary battery that can be charged and discharged by moving lithium ions in a non-aqueous electrolyte between a positive electrode and a negative electrode that occlude and release lithium ions.

  In Patent Document 1, 0.01% by weight to 5% by weight of lithium difluorophosphate is added to a non-aqueous electrolyte of a non-aqueous electrolyte secondary battery, and a film is formed at the interface between the positive electrode and the negative electrode. Techniques for improving the storage characteristics of the are disclosed. That is, in the technique according to Patent Document 1, a film is formed at the interface between the positive electrode and the negative electrode to suppress direct contact between the charged active material and the non-aqueous electrolyte. By doing in this way, decomposition | disassembly of a non-aqueous electrolyte is suppressed and the storage characteristic of a battery is improved.

Japanese Patent Application Laid-Open No. 11-067270

  When lithium difluorophosphate is added to the non-aqueous electrolyte, a film is formed on the surface of the positive electrode. When a film is formed on the surface of the positive electrode in this way, the redox reaction of the nonaqueous electrolytic solution on the surface of the positive electrode can be suppressed, and the amount of gas generated from the positive electrode can be reduced.

  However, even if lithium difluorophosphate is added, depending on the amount of water contained in the electrode body composed of the positive electrode, the negative electrode, and the separator, the reaction between the non-aqueous electrolyte and water may be promoted and the battery characteristics may deteriorate. There is. Specifically, when a non-aqueous electrolyte containing lithium hexafluorophosphate is used, depending on the amount of water contained in the electrode body, the reaction between lithium hexafluorophosphate and water is promoted and hydrogen fluoride is generated. As a result, the battery resistance increases.

  In view of the above problems, an object of the present invention is to provide a method for manufacturing a non-aqueous electrolyte secondary battery that can suppress the generation of gas and suppress an increase in battery resistance.

  A method for producing a non-aqueous electrolyte secondary battery according to one embodiment of the present invention includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, A step of forming an electrode body comprising: a step of housing the electrode body in a battery container; and lithium difluorophosphate so as to have a concentration of 0.025 M or more and 0.05 M or less, including lithium hexafluorophosphate. And a step of injecting the non-aqueous electrolyte to which is added into the battery container. And ratio R (R = A / B) of the amount A (mol) of the added lithium difluorophosphate and the amount of water B (mol) contained in the electrode body before injecting the non-aqueous electrolyte ) Is adjusted to satisfy −0.10 <logR <0.

  In the method for manufacturing a non-aqueous electrolyte secondary battery, the positive electrode active material may contain lithium nickel cobalt manganate.

  The method for manufacturing a non-aqueous electrolyte secondary battery may further include a step of adjusting the amount of water contained in the electrode body.

  In the method for manufacturing a non-aqueous electrolyte secondary battery, a part of the battery container containing the electrode body is opened, and the battery container is left in a predetermined temperature and predetermined humidity environment for a predetermined time. The amount of water contained in the electrode body may be adjusted.

  In the method for manufacturing a non-aqueous electrolyte secondary battery, an electrode body containing moisture is formed as the electrode body, and the electrode body containing moisture is dried for a predetermined time in an environment of a predetermined temperature and a predetermined humidity. The amount of water contained in the electrode body may be adjusted.

  In the method for manufacturing a non-aqueous electrolyte secondary battery, after injecting the non-aqueous electrolyte, the non-aqueous electrolyte secondary battery is charged to a predetermined capacity and left to stand for a predetermined time to perform an activation treatment. You may implement.

  In the method for manufacturing a non-aqueous electrolyte secondary battery, the lithium hexafluorophosphate reacts with water contained in the positive electrode to generate lithium difluorophosphate, and forms a film on the surface of the positive electrode. Also good.

  In the method for manufacturing a non-aqueous electrolyte secondary battery, the electrode body may be a wound electrode body formed by laminating and winding the positive electrode, the separator, and the negative electrode.

  According to the present invention, it is possible to provide a method for manufacturing a non-aqueous electrolyte secondary battery that can suppress generation of gas and suppress increase in battery resistance.

It is a figure which shows the gas generation amount with respect to the density | concentration of the added lithium difluorophosphate (additive), and initial stage IV resistance value. It is a figure which shows the gas generation amount with respect to the moisture content contained in an electrode body. It is a figure which shows the initial stage IV resistance value with respect to the moisture content contained in an electrode body. It is a figure which shows the gas generation amount and the initial IV resistance value with respect to the logarithm of the ratio of the density | concentration of the added lithium difluorophosphate (additive) and the moisture content contained in an electrode body.

Embodiments of the present invention will be described below.
In the method for producing a non-aqueous electrolyte secondary battery according to the present embodiment (hereinafter described as an example of a lithium ion secondary battery), first, a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, An electrode body having a separator disposed between the positive electrode and the negative electrode is formed. Thereafter, the electrode body is accommodated in the battery container, and the nonaqueous electrolytic solution containing lithium hexafluorophosphate and containing lithium difluorophosphate added to a concentration of 0.025M or more and 0.05M or less is used in the battery container. Inject into. Hereinafter, the manufacturing method of a lithium ion secondary battery is demonstrated in detail.

The positive electrode of the lithium ion secondary battery has a positive electrode active material. The positive electrode active material is a material capable of inserting and extracting lithium, for example, lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium nickelate (LiNiO ₂ ), and nickel cobalt that is a mixture thereof. Lithium manganate can be used. An example of the composition of lithium nickel cobalt manganate is LiNi _1/3 Co _1/3 Mn _1/3 O _{2 in} which each metal element is mixed and fired at an equal ratio.

  The positive electrode may contain a conductive material. As the conductive material, for example, carbon black such as acetylene black (AB) and ketjen black, and graphite (graphite) can be used.

  The positive electrode is prepared by, for example, kneading a positive electrode active material, a conductive material, a solvent, and a binder (binder), applying the kneaded positive electrode mixture to a positive electrode current collector, and drying. Can do. Here, as the solvent, for example, an NMP (N-methyl-2-pyrrolidone) solution can be used. As the binder, for example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), or the like can be used. As the positive electrode current collector, aluminum or an alloy containing aluminum as a main component can be used.

  The negative electrode of the lithium ion secondary battery has a negative electrode active material. The negative electrode active material is a material capable of inserting and extracting lithium, for example, a powdery carbon material made of graphite or the like, an amorphous carbon-coated natural graphite in which natural graphite is coated with amorphous carbon, or the like Can be used. Then, similarly to the positive electrode, the negative electrode can be produced by kneading the negative electrode active material, the solvent, and the binder, applying the kneaded negative electrode mixture to the negative electrode current collector, and drying. Here, as the negative electrode current collector, for example, copper, nickel, or an alloy thereof can be used.

  As the separator, for example, a porous polymer film such as a porous polyethylene film, a porous polypropylene film, a porous polyolefin film, or a porous polyvinyl chloride film can be used alone or in combination.

  A separator is interposed between the positive electrode and the negative electrode formed as described above, and an electrode body (rolled electrode body) is formed by winding these laminates. At this time, the electrode body formed by winding the laminate may be crushed from the side surface direction to form a flat wound electrode body.

  Thereafter, the electrode body is accommodated in the battery container. For example, the battery container includes a flat rectangular parallelepiped battery container main body whose upper end is opened, and a lid that closes the opening. The material constituting the battery container is preferably a metal material such as aluminum or steel. Or the container which shape | molded resin materials, such as polyphenylene sulfide resin (PPS) and a polyimide resin, may be sufficient. A positive electrode terminal electrically connected to the positive electrode of the wound electrode body and a negative electrode terminal electrically connected to the negative electrode of the wound electrode body are provided on the upper surface (that is, the lid) of the battery container.

  And the positive electrode lead terminal and the negative electrode lead terminal are respectively provided in the portion where the positive electrode and the negative electrode are exposed at both ends of the wound electrode body (the portion where the positive electrode mixture layer and the negative electrode mixture layer are not present). Connect each terminal electrically. Thereafter, the wound electrode body is accommodated in the container body, and the opening of the container body is sealed using the lid. Thereafter, a non-aqueous electrolyte is injected from a liquid injection hole provided in the lid, and the lithium ion secondary battery can be manufactured by closing the liquid injection hole with a sealing cap.

The nonaqueous electrolytic solution is a composition in which a supporting salt is contained in a nonaqueous solvent. Here, as the non-aqueous solvent, one or two selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like. More than one type of material can be used. Further, lithium hexafluorophosphate (LiPF ₆ ) can be used as the supporting salt.

And in the manufacturing method of the lithium ion secondary battery according to the present embodiment, the concentration of lithium difluorophosphate (LiPO ₂ F ₂ ) in the non-aqueous electrolyte is 0.025 or more and 0.05 M or less. Lithium difluorophosphate is added to the non-aqueous electrolyte. The structural formula of lithium difluorophosphate is shown below.

  At this time, the amount of lithium difluorophosphate added (hereinafter also referred to as additive) A (substance amount, unit is mol), and the electrode body before injecting the non-aqueous electrolyte (that is, the positive electrode) , Negative electrode, and separator), the logarithm (common logarithm) of the ratio R (R = A / B) to the amount of water B (substance in mol, the unit is mol) is −0.10 <logR <0. Try to meet. The amount of water B contained in the electrode body can be measured using the Karl Fischer method.

  The ratio R between the amount A of additive and the amount of water B contained in the electrode body can be changed by adjusting the amount of additive A added or by adjusting the amount of water B contained in the electrode body. it can. For example, the additive amount A can be changed by adjusting the concentration of the additive in the non-aqueous electrolyte.

  When adjusting the water content B contained in the electrode body, a step of adjusting the water content B contained in the electrode body may be further provided. For example, even if the amount of moisture B contained in the electrode body is adjusted by opening a part of the battery container containing the electrode body and leaving the battery container in a predetermined temperature and humidity environment for a predetermined time. Good. In addition, after the electrode body is formed and before the electrode body is accommodated in the battery container, the electrode body is allowed to stand for a predetermined time in an environment of a predetermined temperature and a predetermined humidity so that the amount of water B contained in the electrode body is You may adjust.

  Further, when forming the positive electrode and the negative electrode, a predetermined amount of water is mixed with the positive electrode mixture and the negative electrode mixture to form a water-containing electrode body, and the water-containing electrode body is formed at a predetermined temperature and a predetermined temperature. The amount of water contained in the electrode body may be adjusted by drying for a predetermined time in a humidity environment.

  Moreover, in the manufacturing method of the lithium ion secondary battery concerning this Embodiment, you may implement an activation process, after inject | pouring a non-aqueous electrolyte. The activation process can be performed by charging the lithium ion secondary battery to a predetermined capacity and leaving it for a predetermined time. As a specific example, the lithium ion secondary battery is fully charged (that is, the SOC is 100%), and then the conditioning process is performed. Thereafter, the SOC is kept at 100% and stored in a 60 ° C. environment for a certain period. Thus, the aging process can be performed and the activation process can be performed.

  In the method for manufacturing a lithium ion secondary battery according to the present embodiment, lithium difluorophosphate is added to the non-aqueous electrolyte so that the concentration of lithium difluorophosphate in the non-aqueous electrolyte is 0.025 to 0.05M. Is added. Thus, when lithium difluorophosphate is added to the non-aqueous electrolyte, a film is formed on the surface of the positive electrode. And if a film | membrane is formed on the positive electrode surface, the oxidation-reduction reaction of the nonaqueous electrolyte solution on the positive electrode surface can be suppressed, and the amount of gas generated from the positive electrode can be reduced. At this time, as the concentration of lithium difluorophosphate in the non-aqueous electrolyte increases, the thickness of the coating formed on the surface of the positive electrode increases, so that the amount of gas generated from the positive electrode can be further reduced.

On the other hand, even if lithium difluorophosphate is added, depending on the amount of water contained in the electrode body composed of the positive electrode, the negative electrode, and the separator, the reaction between lithium hexafluorophosphate and water is promoted and hydrogen fluoride is generated. As a result, the battery resistance increases. The reaction of lithium hexafluorophosphate with water is shown below.
LiPF ₆ + 2H ₂ O → LiPO ₂ F ₂ + 4HF (1)

  Thus, lithium hexafluorophosphate reacts with water to produce lithium difluorophosphate and hydrogen fluoride. When the reaction between lithium hexafluorophosphate and water is promoted and the amount of lithium difluorophosphate increases, the amount of lithium difluorophosphate film formed on the positive electrode increases, so the amount of gas generated from the positive electrode decreases. To do. However, when this reaction is promoted, the concentration of hydrogen fluoride in the non-aqueous electrolyte also increases. As the concentration of hydrogen fluoride in the non-aqueous electrolyte increases, chemical erosion of the positive electrode and the negative electrode by hydrogen fluoride proceeds, and deterioration and decomposition of the positive electrode and the negative electrode proceed, so that battery resistance increases.

  Therefore, in the method of manufacturing a lithium ion secondary battery according to the present embodiment, the amount A (mol) of lithium difluorophosphate added to the non-aqueous electrolyte and the electrode body before injecting the non-aqueous electrolyte (that is, The logarithm of the ratio R (R = A / B) to the amount of water B (mol) contained in the positive electrode, the negative electrode, and the separator is set to satisfy −0.10 <logR <0. Thus, by adjusting the amount A (mol) of lithium difluorophosphate and the amount of water B (mol) contained in the electrode body as described above, the reaction of the reaction formula (1) can be efficiently advanced. It is possible to suppress the generation of gas accompanying the oxidation-reduction reaction of the non-aqueous electrolyte, and it is possible to suppress an increase in battery resistance. (See FIG. 4. The range indicated by the arrow in FIG. 4 is the range where the effect of the present invention can be obtained.)

  That is, when the value of logR is small, the proportion of moisture contained in the electrode body is high and the proportion of additive is low. In this case, since the ratio of the moisture contained in the electrode body is high, the reaction of the reaction formula (1) is promoted, the amount of hydrogen fluoride generated increases, and the battery resistance increases. At this time, lithium difluorophosphate is also produced by the reaction of the reaction formula (1). Since water present on the surface of the electrode body is used in the reaction of the reaction formula (1), the lithium difluorophosphate generated by the reaction of the reaction formula (1) is unevenly distributed on the surface of the electrode body.

  Here, the lithium difluorophosphate film formed on the positive electrode is mainly composed of a film derived from lithium difluorophosphate added to the non-aqueous electrolyte (film A), moisture present on the positive electrode surface, and phosphorus hexafluoride. There is a film (coating B) generated by reacting with lithium acid (see reaction formula (1)). And since the membrane | film | coat B is produced | generated using the water | moisture content which exists on the surface of a positive electrode, the direction of the membrane | film | coat B can be formed in the positive electrode surface more efficiently (that is, it is unevenly distributed in the positive electrode surface).

  Therefore, when the value of logR is small, the proportion of the additive is low, but since the lithium difluorophosphate film (film B) derived from the reaction formula (1) can be efficiently formed on the positive electrode surface, Generation of gas accompanying the oxidation-reduction reaction of the electrolytic solution can be suppressed (see FIG. 4).

  On the other hand, when the value of logR is large, the proportion of moisture contained in the electrode body is low and the proportion of additive is high. In this case, since the ratio of the moisture contained in the electrode body is low, the reaction of the reaction formula (1) does not proceed so much and the production amount of hydrogen fluoride is small, so that an increase in battery resistance can be suppressed. In this case, since the ratio of the additive is high, the film formed on the positive electrode surface is mainly a film (film A) derived from lithium difluorophosphate added to the non-aqueous electrolyte. Here, the film (film A) derived from lithium difluorophosphate added to the non-aqueous electrolyte is a film (film formed by reacting water present on the positive electrode surface with lithium hexafluorophosphate. The production efficiency is lower than in B). Therefore, when the value of logR is large, the ratio of the additive is high, but since the lithium difluorophosphate film cannot be efficiently formed on the positive electrode surface, the amount of gas generated increases (see FIG. 4).

  Considering the above points, in the method of manufacturing a lithium ion secondary battery according to the present embodiment, the amount A (mol) of lithium difluorophosphate added to the non-aqueous electrolyte and before injecting the non-aqueous electrolyte The logarithm of the ratio R (R = A / B) to the water content B (mol) contained in the electrode body satisfies −0.10 <logR <0. Thus, the reaction of the reaction formula (1) is efficiently advanced by setting the ratio of the amount A (mol) of lithium difluorophosphate and the amount of water B (mol) contained in the electrode body to an optimum ratio. It is possible to suppress the generation of gas accompanying the oxidation-reduction reaction of the non-aqueous electrolyte, and it is possible to suppress an increase in battery resistance.

  Next, examples of the present invention will be described.

<Production of lithium ion secondary battery>
The positive electrode was produced by applying a positive electrode mixture containing a positive electrode active material to a positive electrode current collector and drying it. 89% by weight of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a positive electrode active material, 8% by weight of polyvinylidene fluoride (PVdF) as a binder, and 3% by weight of acetylene black (AB) as a conductive material Were respectively kneaded to prepare a positive electrode mixture. Thereafter, the positive electrode mixture was applied onto an aluminum foil and dried, and then processed into a desired thickness and width.

  The negative electrode was produced by applying a negative electrode mixture containing a negative electrode active material to a negative electrode current collector and drying it. A negative electrode mixture was prepared by kneading 98% by weight of graphite as a negative electrode active material, 1% by weight of styrene butadiene rubber (SBR) as a binder, and 1% by weight of carboxymethyl cellulose (CMC) as a thickener. Then, after apply | coating this negative electrode mixture on copper foil and drying, it processed into the desired thickness and width | variety.

  A separator was interposed between the positive electrode and the negative electrode formed as described above, and an electrode body (rolled electrode body) was formed by winding these laminates. Then, a positive electrode lead terminal and a negative electrode lead terminal are respectively provided in a portion where the positive electrode and the negative electrode are exposed at both ends of the electrode body (a portion where the positive electrode mixture layer and the negative electrode mixture layer are not provided), and provided on the lid of the battery container. The positive electrode terminal and the negative electrode terminal are electrically connected to each other. Thereafter, the electrode body was accommodated in a battery container and sealed with a lid.

  Then, in order to adjust the amount of water contained in the electrode body produced as described above, it was left in a high-humidity tank having a temperature of 25 ° C. and a humidity of 75% for a predetermined time with the injection hole opened. Then, the moisture content of the positive electrode, the negative electrode, and the separator was measured using the Karl Fischer method, and this measured moisture content was used as the moisture content contained in the electrode body. Since the measurement by the Karl Fischer method is a destructive inspection, a plurality of samples were prepared, and the moisture content contained in the electrode body was measured using one of these samples. Table 1 below shows the relationship between the time left in the high-humidity tank and the amount of water contained in the electrode body. As shown in Table 1, the amount of water contained in the electrode body increased as the time left in the high humidity tank increased.

Thereafter, a non-aqueous electrolyte was injected from a liquid injection hole provided in the lid, and the liquid injection hole was closed with a sealing cap. In the non-aqueous electrolyte, LiPF ₆ as a supporting salt was contained at a concentration of 1.1 M (mol / L) in a mixed solvent containing EC, DMC, and EMC at a volume ratio of 30:40:30, respectively. I used something. A predetermined amount of lithium difluorophosphate (additive) was added to the non-aqueous electrolyte.

  After producing a lithium ion secondary battery, activation treatment was performed. In the activation process, the lithium ion secondary battery is fully charged (SOC = 100%), then the conditioning process is performed, and then the SOC is maintained at 100% and stored in a 60 ° C. environment for a certain period of time. Processed and carried out. After performing the activation process, an internal pressure sensor was attached.

<Measurement of initial IV resistance value>
The initial IV resistance value (−30 ° C.) of the lithium ion secondary battery produced as described above was measured. That is, before conducting the storage test, the SOC of the lithium ion secondary battery was adjusted to 15%, the ambient temperature was set to −30 ° C., and each battery was left for 3 hours. Thereafter, discharging was performed at 2C at -30 ° C for 10 seconds, and the voltage value 10 seconds after the start of discharge was plotted to obtain an initial IV resistance value (mΩ) at -30 ° C, which was defined as battery resistance.

<Measurement of gas generation amount>
After measuring the initial IV resistance value, the gas generation amount (gas generation amount after 50 days) when the lithium ion secondary battery was stored in an atmosphere at 60 ° C. for 50 days was measured. The amount of gas generated was determined using the internal pressure in the battery container determined by the internal pressure sensor.

<Test 1>
In order to investigate the relationship between the amount of lithium difluorophosphate added and the amount of gas generated, sample A in which the concentration of lithium difluorophosphate in the non-aqueous electrolyte is 0.025M, and sample B which is 0.05M Prepared. At this time, the amount of water contained in the electrode body was 100 mg. That is, a lithium ion secondary battery left for 18 hours in a high humidity tank was used. Table 2 below shows the relationship between the electrolyte composition of each sample, the amount of water contained in the electrode body, and the concentration of lithium difluorophosphate.

<Test result 1>
FIG. 1 and Table 3 show the measurement results of the initial IV resistance values (−30 ° C.) and the gas generation amounts (gas generation amounts after 50 days) of Samples A and B prepared as described above.

  As shown in FIG. 1 and Table 3, as the concentration of lithium difluorophosphate increased, the amount of gas generated decreased. That is, it is considered that when the concentration of lithium difluorophosphate in the non-aqueous electrolyte increases, the amount of the film formed on the surface of the positive electrode increases, and the amount of gas generated from the positive electrode is further reduced. Therefore, the gas generation | occurrence | production suppression effect of the positive electrode membrane | film | coat formed by the additive origin was confirmed. Moreover, the initial IV resistance value (−30 ° C.) decreased as the concentration of lithium difluorophosphate increased.

<Test 2>
In order to investigate the influence of moisture on lithium difluorophosphate as an additive, sample C containing 70 mg of water, sample D containing 100 mg of water, sample E containing 120 mg of water, and 150 mg of water Sample F and Sample G with a water content of 180 mg were prepared. At this time, the concentration of lithium difluorophosphate in the non-aqueous electrolyte was 0.05M. Table 4 below shows the relationship between the electrolytic solution composition of each sample, the concentration of lithium difluorophosphate, and the amount of water contained in the electrode body.

<Test result 2>
The measurement results of the initial IV resistance value (−30 ° C.) and the gas generation amount (gas generation amount after 50 days) of the samples C to G prepared as described above are shown in FIG. 2, FIG. 3 and Table 5. .

  As shown in FIG. 2 and Table 5, the amount of gas generation decreased as the amount of water contained in the electrode body increased. This is because when the amount of water contained in the electrode body increases, the reaction between water contained in the positive electrode and lithium hexafluorophosphate contained in the non-aqueous electrolyte (see reaction formula (1)) is promoted and formed on the positive electrode. This is because the amount of the lithium difluorophosphate film formed is increased.

  On the other hand, as shown in FIG. 3 and Table 5, when the amount of water contained in the electrode body increased from 100 mg, the initial IV resistance value (−30 ° C.) increased. This is because when the amount of water contained in the electrode body increases, the reaction between the water contained in the electrode body and lithium hexafluorophosphate contained in the non-aqueous electrolyte (see reaction formula (1)) is promoted. This is probably because the concentration of hydrogen fluoride in the electrolyte increased.

For each sample shown in Test Result 1 (Table 3) and Test Result 2 (Table 5), the amount A (mol) of lithium difluorophosphate added to the non-aqueous electrolyte and the amount of water B contained in the electrode body The ratio R (R = A / B) to (mol) was determined. The amount A (mol) of lithium difluorophosphate was determined using the concentration of lithium difluorophosphate and the amount of non-aqueous electrolyte injected into the battery container. FIG. 4 and Table 6 show the measurement results of the initial IV resistance value (−30 ° C.) and the gas generation amount (gas generation amount after 50 days) with respect to the logarithm of these ratios R.

  As shown in FIG. 4 and Table 6, the ratio R (R = A / B) of the amount A (mol) of lithium difluorophosphate added to the non-aqueous electrolyte and the amount of water B (mol) contained in the electrode body ) Satisfies −0.10 <logR <0, the gas generation amount is reduced, and the initial IV resistance value is further reduced. That is, in this range, since the ratio of the amount A (mol) of lithium difluorophosphate and the amount of water B (mol) contained in the electrode body is the optimum range, the reaction of the reaction formula (1) proceeds efficiently. It is thought that.

  The present invention has been described with reference to the above-described embodiment and examples. However, the present invention is not limited only to the configurations of the above-described embodiment and examples. It goes without saying that various modifications, corrections, and combinations that can be made by those skilled in the art within the scope of the invention are included.

Claims (8)

Forming an electrode body having a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a separator disposed between the positive electrode and the negative electrode;
Accommodating the electrode body in a battery container;
Injecting a non-aqueous electrolyte containing lithium hexafluorophosphate and having lithium difluorophosphate added to a concentration of 0.025M or more and 0.05M or less into the battery container,
Ratio R (R = A / B) of the amount A (mol) of the added lithium difluorophosphate and the amount of water B (mol) contained in the electrode body before injecting the non-aqueous electrolyte Logarithm satisfies −0.10 <logR <0,
A method for producing a non-aqueous electrolyte secondary battery.   The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode active material includes lithium nickel cobalt manganate.   The method for producing a nonaqueous electrolyte secondary battery according to claim 1, further comprising a step of adjusting the amount of water contained in the electrode body.   Opening a part of the battery container containing the electrode body, and adjusting the amount of water contained in the electrode body by leaving the battery container for a predetermined time in an environment of a predetermined temperature and a predetermined humidity, The manufacturing method of the non-aqueous-electrolyte secondary battery of Claim 3.   Forming an electrode body containing moisture as the electrode body, and adjusting the amount of moisture contained in the electrode body by drying the electrode body containing moisture for a predetermined time in an environment of a predetermined temperature and a predetermined humidity; The manufacturing method of the non-aqueous-electrolyte secondary battery of Claim 3.   6. The activation process is performed by charging the non-aqueous electrolyte secondary battery to a predetermined capacity after leaving the non-aqueous electrolyte and allowing the battery to stand for a predetermined time. The manufacturing method of the non-aqueous-electrolyte secondary battery as described in 2 ..   The said lithium hexafluorophosphate reacts with the water contained in the said positive electrode, produces | generates a lithium difluorophosphate, and forms the membrane | film | coat on the surface of the said positive electrode. A method for producing a water electrolyte secondary battery.   The non-aqueous electrolyte according to any one of claims 1 to 7, wherein the electrode body is a wound electrode body formed by stacking and winding the positive electrode, the separator, and the negative electrode. A method for manufacturing a secondary battery.

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